Continuous bleaching process



Patented May 29, 1951 UNITED STATES L'AP-ll-Til'NT 'OFFICE 2555,99? Y l CoNTINUoUs BLEAI 'PizocEss Judson H. Sanders, Wyoming,"0hio, assignor to The Procter & Gamblee'C`xip'a`.ny,` Cincinnati, 0hio,acorporation of Ohio i l H n y 'Aalliauoa january 24, 1i7g`sriarNo. 723,989

soybean oil are commercially reiined and bleached bybatch methods, the customary steps include: v1(a,) adding a dilute solution of caustic soda to lan agitated refining kettle nearly full of the ycrude oil, the amount of the alkali being somewhat more than that required to neutralize the free Yfatty acids and to react with coloring matter and albuminous impurities that are present in the crude oil, 1(1)) continuing the agitation 4while raising the temperature of the oil gradually until the reiining foots begin tomelt and to coalesce in visible masses, i. e. to break, 1(c) discontinuing the heating and agitation .and allowing the foots to settle out of the refined oil, and after an interval drawing off the` reiined oil; 2(a) permitting this oil to settle again for several hours to substantially remove remaining traces of foots, 2(1)) filtering the settled oil through kieselguhr yor other filtering `medium to remove traces of moisture and dissolved soap; 3(a) adding to the thus clarified oil in an agitated bleach tankV a color absorbing material such' as ullers earthV or activated vclay and agitating for a period of time at a slightly elevated temperature, 3(1)) removing the bleaching earth from the oil by filtration.

.For some years thevegetable oil refining industry has to a'great extent been practicing .a

.continuous refining process in which continuous .mixing andheating/during ow through a small tank has replaced the above steps 1( a) Vand 1(1)), and centriiuging Vhas replaced the gravity settling and decanting ,of step 1(0) The bleaching operation, steps ,3(01) yand 3(1)), is stil1.per-

(Graco-#427) .provide a practical and economical continuous formedas va batch process by a major portion ofy the industry. l, Continuous reiining and centrifuging has not eliminated they necessity of further clarication of the oil before bleaching, such asis provided watercontaining' traces of dissolved soap, Vwhich is "detrimental tol good bleaching as currently practiced. Hence when continuousv water washing of rened oil followed by centrifuging is Apracticed, it is customary to follow this by drying the oil, usually under vacuum in order to avoid "overheating, prior to bleachingthis being the "normal practice Whether the bleaching is to be Lby batch or by a continuous method. Upon drying the oil, the traces Vof soap which it contains lare dehydrated, and after the bleaching the dehydrated soap is lt'ered out along with the' spent bleaching earth.

The present Ainvention arises from the discovery that unexpected vand advantageous results, in the form of lighter bleached oil colors, are obtained by rearranging the steps of 'the continuous water washing and bleaching process,` to accomplish the absorption of coloring matter by the bleaching clay before instead of after the oil is L dried.

irismybeuef that the dehydration of the traces of soap contained in Water Washedoilin prior' artprocesses results in an extraction of col- 25 oring matter by the oil from the,l soap, and that the lower bleach colors obtained by my process fare largely the result ofeither preventing this color extraction or delaying it until bleaching l clay isdispersed throughoutthe oil in a position to absorb the color released by the soap.

Objects .of thempresent invention are to render `-unnecessary the step of dryingbefore bleaching,

toayoidthe extraction of coloringmatter by the Aoil from ,traces of vsoap in the oil, to improve the color removal of the bleachingoperation, and to washing and bleachingprocess., Y

T he accompanying ow chart indicates the order ofthe steps ofthe process. The solid lines ,with arrowsv show the. `preferred sequence, and

the dotted` lines indicate two independent optional alternatives, (A) andiB).

The following is anexample of the practice of by steps 2(a) and 2(1)), and these steps are still V common practice prior to bleaching .by batch methods. A continuous procedure Ywhich accom- .plishes most of the objectives ofA these steps 2(a) and 2(1)) is continuous water washing followed the oil wet with dissolved and minutely dispersed .by `a secondA centrifuging. This however, leaves my invention using-in this instance freshly caus- Y .tic.-.relned cottonseed oil.A The o il is 'continuously supplied from the foots removing centrifuges, in jthis case at a, temperature inthe neighborhood of .130 F., and is continuously mixed and .agitated for, about a minute @more in a closed chamber with av continuous stream of water amounting to about per cent more or less of the Weight of oil, and the mixture is then continuously fed through another centrifuge to remove the aqueous phase containing dissolved soap and other impurities. The wet oil issuing from this second centrifuge is continuously admixed with a continuously proportioned supply of bleaching clay, preferably supplied in the form of a slurry of clay in previously refined and bleached oil, and this mixture is passed through a zone of vigorous mechanical agitation, requiring some minutes for this passage, and thence through a suitable heater where its temperature is raised to about 175 F. From this heater the wet oil-earth mixture passes to a ilash tank which is maintained under a reduced pressure which should be below the vapor pressure of the water in the oil at the temperature of the flash-dried oil. In this flash tank the water contained in the mixture vaporizes and is drawn off through a vapor exit leading from the top of the Vaporizing chamber. The dried oil-earth mixture, or slurry, now at a temperature reduced to about 160 F. as a result of the evaporative cooling, is then sent to a suitable filtering apparatus for removal of the bleaching earth. A rotary filter may be used, or an alternating pair of filter presses of a conventional design. It may be desirable to precool the oil before filtration in order to avoid any deleterious oxidation upon its contact with the atmosphere.

In the practice of my process, the oil during its contact with the bleaching clay may have temperatures hitherto acceptable for bleaching by the conventional practice above referred to, say from 120 F. to 220 F., and the time of contact should be suiicient to accomplish effective color removalat least one minute under conditions of good agitation. The oil temperature at the beginning of its ash drying should preferably be between 140 F. and 220 F.

The process may be 'varied in a number of respects Without departing from the spirit or scope of the invention. For example, the heating of the wet oil prior to flash drying may be done before the addition of bleaching clay instead of after. The ltration of the bleached oil, to remove the bleaching clay and traces of soap together with the coloring matter absorbed by the clay and the soap, may even be done before the flash drying step-although this brings about obvious iiltration diiiiculties if enough moisture is present to make the lter cake slimy.

The process is applicable to all caustic rened glyceride fats and oils, including animal fats such as lard and tallow, vegetable fats and oils such as palm oil, coconut oil, cottonseed oil, peanut oil, and soybean oil, and marine oils such as whale oil, herring oil, and sardine oil. Its advantage in producing lighter colored bleached oil is outstanding in the case of oils having a high ratio of coloring matter in the refining foots as compared With the amount of color in the refined oil. Thus the process is particularly advantageous when employed in the processing of cottonseed oil. The process is particularly appropriate 'as applied to freshly rened oil, but will find application also to settled refined oils `which still contain traces of refining foots.

The following table, based upon the processing of three identical portions of a lot of freshly rened oil, gives a comparison of the steps and results characteristic of the present process (column a), as compared with a prior art process in 4 which the water washed oil is vacuum dried before bleaching (column b), and also compares these two procedures with batch clarification and bleaching (column c).

(l) Continuously refine crude cottonseed oil, and centrifuge.

(2) Water Wash 2 min. at 140 F. with 20% Settle 6 hrs. and deby weight of water, centrifuge, and cant,filterthrough heat to 180 F. guhr (Lovibond color 35Y 6.53)

(3) Bleach 15 min. Vacuum dry at 5 Bleach l5 min. at with 3% Pke's min. Hg pressure 180 F. with 3% Peak fullers (Lovibond color Pikcs Peak fulearth. 50Y 8.0R). lers earth.

(4) Vacuum dry at 5 Bleach 15 min. at mm. Hg pres- 180 F. with 3% sure. Pikes Peak fullers earth.

(5) Filter Filter Filter Lovibond color Lovibond color Lovibond color 20Y 2.5K. 2OY 2.9R. 20Y 2.6K.

(a) (b) (C) Thus the process of the present invention produces bleached oil of materially lighter color than the prior continuous process, and fully as light as the slower batch process.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. The improvement in the continuous process of bleaching caustic refined, water washed, and centrifuged glyceride oil which comprises effectively contacting the Washed and centrifuged oil, containing residual dissolved and entrained moisture, with bleaching clay for at least one minute to cause the absorption of coloring matter from the oil by the clay, delaying the removal of the moisture contained in the oil-clay mixture until effective color absorption has occurred, and then removing said moisture by vacuum drying and said clay by filtration from said oil.

2. The process of claim 1 in which the vacuum drying of the decolorized oil precedes the ltration to remove the clay.

3. The process of claim 1 in which the filtration to remove the clay from the decolorized oil precedes the vacuum drying of the oil.

4. The continuous process of bleaching caustic rened, water washed, and centrifuged glyceride oils which comprises: continuously and intimately admixing a owing stream of the washed and centrifuged and undried oil with a minor proportion of bleaching clay; passing this mixture through a zone of vigorous mechanical agitation while retaining the moisture in the mixture until effective color removal has occurred; continuously introducing the wet oil-clay slurry, heated to a temperature in the range F. to 220 F., into an enclosed drying chamber which is maintained, by the continuous withdrawal of water vapor, at a pressure below the vapor pressure of the water in the oil at the temperature of the oil after the evaporative cooling which occurs in said chamber; and continuously filtering the bleaching clay from the resulting vacuum dried oil.

5. In the continuous refining, Water washing, and bleaching of glyceride oils the steps which comprise bleaching undried water washed refined oil with bleaching clay in the presence of residual moisture, followed by the steps, in different order 5 of removing said moisture by Vacuum drying and said clay by filtration' from:r the bleached oil.

6. The process of claim 1- in which the caustic rened glyceride oil is cottonseed oil.

7. The process of claim 4 in which the caustic 3 rened glyceride oil is cottonseed oil.

JUDSON H. SANDERS.

REFERENCES CITED The following references are of record in the l file of this patent:

6 UNITED STATES PATENTS Name Date -1,`70'.324 Odeen Mar.v19,A 1929 157253995 Bayns Aug; 27, 1929 l234218,1(132 King et al Sept." 30, 1947 OTHER REFERENCES Gillies- Oil and Colour Trades Journal, Februarym, 1944, pages 24U-243. o Bail`ey0i1 and Fat Products (1945) Interscience Pub., page 530. 

1. THE IMPROVEMENT IN THE CONTINUOUS PROCESS OF BLEACHING CAUSTIC REFINED, WATER WASHED, AND CENTRIFUGED GLYCERIDE OIL WHICH COMPRISES EFFECTIVELY CONTACTING THE WASHED AND CENTRIFUGED OIL, CONTAINING RESIDUAL DISSOLVED AND ENTRAINED MOISTURE, WITH BLEACHING CLAY FOR AT LEAST ONE MINUTE TO CAUSE THE ABSORPTION OF COLORING MATTER FROM THE OIL BY THE CLAY, DELAYING THE REMOVAL OF THE MOISTURE CONTAINED IN THE OIL-CLAY MIXTURE UNTIL EFFECTIVE COLOR ABSORPTION HAS OCCURRED, AND THEN REMOVING SAID MOISTURE BY VACUUM DRYING AND SAID CLAY BY FILTRATION FROM SAID OIL. 